Stamps are used in a variety of applications and for various purposes. Areas of stamp use include micro contact printing (μCP) and nano transfer printing (nTP). Contact, or transfer, printing relies on surface chemistries for transferring thin films from the raised regions of a stamp to a substrate when these two elements are brought into physical contact. This technique is an additive process utilizing patterning approaches referred to as soft lithography. An article entitled “Printing meets lithography: Soft approaches to high-resolution patterning,” by B. Michel et al., IBM J. Res. & Dev. Vol. 45 No. 5 Sep. 2001, describes the use of an elastomer stamp in micro contact printing. The described elastomer stamp (a.k.a. hybrid printing stamp) is composed of a patterned elastomeric layer attached to a compressible back plane of supporting material (such as a metal), as illustrated in FIG. 1A. The patterned elastomeric layer of the stamp is inked and then printed onto a hard substrate, forming a monolayer of ink on the hard substrate, as illustrated in FIG. 1B. Transfer printing utilizing such a stamp is performed with the application of only a small pressure.
In contrast to contact printing, embossing is an imprinting process that displaces or molds a layer of material with a stamper. The imprinting process requires a greater amount of applied pressure than with stamps used in contact printing. A trend in embossing is the development of nano imprint lithography (NIL) techniques. NIL techniques are being used in the disk drive industry to produce discrete track recording (DTR) magnetic disks. DTR disks typically have a series of concentric raised areas (a.k.a. hills, lands, elevations, etc.) storing data and recessed areas (a.k.a. troughs, valleys, grooves, etc.) that provide inter-track isolation to reduce noise. Such recessed areas may also store servo information. The recessed areas separate the raised areas to inhibit or prevent the unintended storage of data in the recessed areas.
NIL involves the use of a pre-embossed hard forming tool (a.k.a. stamper, embosser, etc.) having an inverse (negative replica) of a DTR pattern. The stamper is pressed onto a thin layer of polymer on a disk substrate. The stamper and polymer/substrate may each be heated, coupled and then the stamper is removed leaving an imprint of the DTR pattern on the polymer layer.
One requirement of an NIL technique in the production of DTR magnetic disks is the ability to produce sub 100 nanometer (nm) features in a reliable way. In the imprinting process, the polymer thickness may typically be in the range of 40 to 500 nm, which may be less than the thickness variation of a stamper and the polymer/substrate surface. NIL requires application of a stamper that allows for good compliance or parallelism between the polymer/substrate surface and the stamper surface. The compliance between the surfaces is limited by surface morphology of the imprinted surface and also by the thickness of the stamper. One problem with conventional NIL stampers, which are typically around 300 microns thick, is that they may not provide for good compliance between the disk surface and the stamper surface due to their thickness. While it is possible to increase compliance by reducing the thickness of the stamper, such an approach may not be acceptable since a very thin stamper would be difficult to handle during its formation (such as during a plating operation) and also during mounting of the stamper into a press system.
A problem with using the patterned elastomer layer printing stamps or hybrid printing stamps described above for imprinting operations is that such stamps may not be sufficiently hard for embossing operations. Such stamps may be too soft for generating sharp and fine grooves or other similar embossed structures that may be need for imprinting operations and may not have sufficient durability for the large number of imprints performed in manufacturing. Such stamps may be limited to use in contact printing operations that utilize low stamping pressure.
One patent, U.S. Pat. No. 6,517,995, describes the use of an elastomeric stamp in a liquid embossing process. In such an embossing process, a thin film of material is deposited on a substrate. The deposited material is either originally present as a liquid or subsequently liquefied prior to embossing. The material is patterned by embossing at a low pressure using a patterned elastomeric stamper. The patterned liquid is then cured to form a functional layer. Such a stamper, however, may be limited to use only with a liquid embossing process that utilizes a low stamping pressure and a liquid embossing substance.